U-Shaped Stairs with Landing: Dimensions and Plan
A U-shaped stair is two parallel flights joined by a half landing that turns you 180°. Make the landing at least as deep as the flights are wide, keep every riser and run inside your code, and open the floor above the landing and the upper flight for headroom. The footprint is roughly two flight widths plus the gap between them, by the landing depth plus the run of the lower flight.
Summary table
| Rule | Imperial | Metric | Source |
|---|---|---|---|
| Half landing, Canada | at least the stair width, both ways | at least the stair width, both ways | NBC 9.8.6.3.(1) |
| Half landing, England | at least the smallest flight width, both ways | same | Approved Document K, 1.20 |
| Half landing, US | at least the flight width across the direction of travel | same | IRC R311.7.6 |
| Half landing, Australia | 29 9/16 in long, measured 19 11/16 in from the inside edge | 750 mm, measured 500 mm from the inside edge | NCC 11.2.5 |
| Flight width, minimum | 36 in (US), 33 7/8 in (Canada) | 914 mm, 860 mm | IRC R311.7.1, NBC 9.8.2.1 |
| Headroom, minimum | 6 ft 8 in (US), 76 13/16 in (Canada), 78 3/4 in (England) | 2032 mm, 1950 mm, 2.0 m | IRC R311.7.2, NBC 9.8.2.2, AD K 1.11 |
| Rise of one flight, maximum | 12 ft 7 in (US), 12 ft 1 5/8 in (Canada) | 3835 mm, 3.7 m | IRC R311.7.3, NBC 9.8.3.3 |
| Guard along the void when the drop exceeds | 30 in within 36 in (US), 23 5/8 in within 47 1/4 in (Canada) | 762 mm within 914 mm, 600 mm within 1.2 m | IRC R312.1.1, NBC 9.8.8.1 |
IRC numbers are from the 2021 edition; the 2024 edition moves stairways to R318.7 with the same values.
When a U-shaped stair makes sense
A U stair folds a straight run in two: the example below needs 88 1/16 in (2237 mm) of length where a straight stair would need 121 3/4 in (3092 mm). The landing gives a rest and shortens any fall, and the top arrives back above the starting end. The price is width for two flights, a gap or wall between them, a landing to frame and a bigger floor opening. In a house, the U is chosen for space: a single flight rarely reaches the maximum rise.
Landing size: the rule that sets the footprint
Landing depth is measured perpendicular to the nosings (NBC 9.8.6.3.(3)), from the landing edge to the back wall.
- Canada: a landing must be at least as wide and as long as the width of the stair (9.8.6.3.(1)). The 860 mm (33 7/8 in) shortcut of 9.8.6.3.(2) only covers landings that do not turn or turn less than 90°; a half landing turns 180°. Details in the Canada stair code guide.
- England: every landing is at least as wide and as long as the smallest width of the flight (Approved Document K, 1.20).
- United States: the landing's width perpendicular to the direction of travel must equal at least the flight width (R311.7.6). On a half landing you walk along the back wall, so the landing depth is the width across that path: plan it at least as deep as the flights are wide. The 36 in (914 mm) minimum depth is written for straight runs. More in the IRC stair code guide.
- Australia: 750 mm, measured 500 mm from the inside edge where the direction changes (11.2.5).
The landing's long side spans both flights and the gap. Put the landing at a whole number of risers; splitting near the middle, 6 + 7 for 13 risers, makes the two flights alike. The arithmetic is in how to calculate stairs.
The void between the flights
Between the flights you can build a wall, leave a narrow gap or open a wide well. Where the drop from the upper flight or the landing exceeds 600 mm (23 5/8 in) in Canada, or 30 in (762 mm) in the US, within the distances in the table, that side needs a guard. Its openings must stop a 100 mm sphere in Canada (9.8.8.5) and a 4 3/8 in (111 mm) sphere along an IRC stair (R312.1.3).
In Stair3D, the room width minus the two flights is the void, and the upper flight and its guard never pass over the lower flight.
Headroom and stairwell opening
Headroom, measured vertically from the nosing line, pinches in two places when the flights sit side by side: at the foot of the stair, where the floor above begins, and in any passage under the landing.
The floor above stays open over the landing and the whole upper flight. The opening length is about the landing depth plus the run of the upper flight, plus the nosing and the riser board. In the example below: 36 3/8 + 6 × 10 1/16 + 1 + 3/4 = 98 1/2 in (2502 mm), from the back wall to the face of the header.
Worked example: Stair3D's default U stair
| Item | Imperial | Metric |
|---|---|---|
| Floor to floor | 97 1/2 in | 2476.5 mm |
| Risers: 6 below the landing, 7 above | 13 × 7 1/2 in | 13 × 190.5 mm |
| Landing height | 45 in | 1143 mm |
| Run, 2R + G, angle | 10 1/16 in, 25 1/16 in, 36.7° | 255.6 mm, 636.6 mm, 36.7° |
| Lower flight: 5 treads, big step / small step | 42 3/4 in wide | 1086 mm wide |
| Upper flight: 6 open treads on two cut stringers | 43 in clear | 1092 mm clear |
| Landing depth: lower flight / upper flight | 36 3/4 in / 36 3/8 in | 933 mm / 924 mm |
| Footprint | 87 1/4 × 88 1/16 in | 2216 × 2237 mm |
| Stairwell opening, length | 98 1/2 in | 2502 mm |
| Headroom at the foot, under the floor above | 86 1/2 in | 2197 mm |
| Handrail and guard height | 36 in | 914 mm |
Now check the landing: 36 3/8 in (924 mm) deep for 43 in (1092 mm) flights. That is enough for a straight landing, but short of the half-landing rule in Canada and England. Running the same stair through Stair3D with one change gives two compliant layouts in the same room:
- Narrow the flights to 36 3/4 in and 36 3/8 in (933 and 924 mm), above the 860 mm minimum, with a 12 5/8 in (321 mm) void between them. The footprint does not change.
- Keep the 43 in flights and lengthen the opening to 105 1/8 in (2670 mm) for a 43 in (1092 mm) landing. The footprint grows to 87 1/4 × 94 5/16 in (2216 × 2396 mm).
The open treads of the upper flight leave 5 3/4 in (146 mm) gaps: allowed in a Canadian house, too wide for the IRC (4 in sphere above 30 in), England (100 mm) or Australia (125 mm), where riser bars or closed risers fix it.
How Stair3D fits a U stair into your opening
Enter your walls, room width, stairwell opening and floor heights; Generate looks for the riser count, landing and run that fit and pass the checks, then shows the stair in 3D with a cut list, a DXF per part, a STEP file and a parametric Fusion 360 module. Either flight can be a bleacher stair, big step / small step, with every other step widened into the space beside the other flight; in the example the wide steps keep 15 in (381 mm) of clearance under the upper flight and are not part of the walking width. Today the checks follow the Canadian rules.
Common mistakes
- Framing a 36 in landing for wider flights.
- Leaving the open side of the upper flight without a guard.
- Running the upper flight's stringer or guard over the lower flight, which steals headroom.
FAQ
How big does the landing of a U-shaped stair need to be?
At least as deep as the flights are wide in Canada (NBC 9.8.6.3) and England (Approved Document K, 1.20). The IRC's width across the direction of travel (R311.7.6) amounts to the same on a half landing. Australia requires 750 mm.
How much space does a U-shaped stair need?
Width: two flights plus the void. Length: the nosing, the lower flight's run and the landing depth. The example takes 87 1/4 × 88 1/16 in (2216 × 2237 mm).
How long is the stairwell opening for a U stair?
About the landing depth plus the run of the upper flight: 98 1/2 in (2502 mm) in the example, 105 1/8 in (2670 mm) with a full 43 in landing.
How many steps go before the landing?
Any whole number of risers; splitting near the middle gives two similar flights.
Do U-shaped stairs need a guard between the flights?
Yes, on any open side where the drop exceeds 600 mm in Canada or 30 in in the US, unless a wall closes it.
Stair3D gives you a design and a code check to guide your work. Check the measurements on site and with your local building authority before cutting.